Lattice welding robot and method for the lattice welding

Abstract

A lattice welding robot detects an X-axis slide position of Xp by an arc sensor of a welding torch, compares the value of Xp with a reference value of X0 by a comparator, calculates a differential value of the value of Xp by a differentiator and computes a travel speed correction amount DELTA V from a difference between a comparator output value and a differentiator output value by a computing unit. The correction amount DELTA V is added to an initial speed of each of inside wheels and outside wheels of a welding carriage to control each of driving motors for the inside wheels and the outside wheels by an adding speed command Vin and an adding speed command Vout, respectively. Thereby, a rough guidance for the welding carriage to trace a weld line is performed.

What is claimed is: 
     
       1. A lattice welding robot comprising: a self-driven welding carriage having a pair of driving wheels which can be controlled independently to run and turn said welding carriage;   a welding torch mounted on said carriage for rotating a welding wire at a torch tip end at a high speed;   an X-axis slide mechanism for moving said welding torch in a horizontal direction relative to said carriage;   a Y-axis slide mechanism for moving said welding torch in a torch axis direction to keep a torch height constant;   a detector for detecting a corner portion of a member material to be welded so as to enable a turning operation at the corner portion to be carried out;   axis direction control means for controlling an X-axis direction position and a Y-axis direction position of the welding torch by using an arc sensor;   setting means for setting said welding carriage at a weld start position relative to said material to be welded; and   a rough guidance controller for controlling a travel direction of said welding carriage, said rough guidance controller comprising an X-axis detector for detecting an X-axis slide position of said welding torch when said welding torch is controlled to be positioned at a center of a welding groove by said arc sensor;   a comparator for comparing said detected X-axis slide position with a preset reference value of said X-axis slide position of said welding torch;   a calculating unit for calculating a differential value of said detected X-axis slide position of said welding torch; and   a control unit for controlling an advancing direction of said welding carriage by supplying independently an adding speed signal to said pair of driving wheels derived from the outputs of said comparator and said calculating unit so as to cause said carriage to run substantially parallel with said weld line and to keep a substantially constant distance between said welding carriage and said weld line, whereby said X-axis direction slide position of said welding torch is located at a proper position for welding.     
     
     
       2. The robot of claim 1, wherein said detector comprises a proximity switch. 
     
     
       3. The robot of claim 2, wherein said detector further comprises an encoder for detecting a turning angle of said carriage. 
     
     
       4. The robot of claim 3, wherein said setting means comprises a limit switch. 
     
     
       5. The robot of claim 1, wherein said setting means comprises a limit switch. 
     
     
       6. The robot of claim 1, wherein said X-axis slide mechanism and said Y-axis slide mechanism each comprise a ball screw feed mechanism. 
     
     
       7. The robot of claim 1, wherein said rough guidance controller includes; a first amplifier which receives a speed signal which is calculated from a deviation of said X-axis slide position of said welding torch; and a second amplifier which receives a signal which is a differentiated value of said X-axis slide position of said welding torch; the outputs of said amplifiers being coupled to said control unit. 
     
     
       8. The robot of claim 7, wherein said first and second amplifiers have different gains. 
     
     
       9. The robot of claim 7, wherein said control unit of said rough guidance controller includes two adders which respectively add an initial speed V 0  of said welding carriage to outputs from said first and second amplifiers to produce respective signals for driving respective driving motors of said driving wheels. 
     
     
       10. The robot of claim 9, wherein said initial speed is outputted from a standard welding speed setting unit. 
     
     
       11. The robot of claim 9, wherein said driving wheels comprise a pair of inside drive wheels and a pair of outside drive wheels, said inside drive wheels being closer to the welding groove than said outside drive wheels. 
     
     
       12. The robot of claim 1,wherein said driving wheels comprise a pair of inside drive wheels and a pair of outside drive wheels, said inside drive wheels being closer to the welding groove than said outside drive wheels. 
     
     
       13. A method of controlling a lattice welding robot during a welding operation, comprising: providing a self-driven welding carriage having a pair of driving wheels which can be controlled independently to run and turn said welding carriage, said carriage having a welding torch mounted on said carriage for rotating a welding wire at a torch tip end at a high speed;   moving said welding torch in a horizontal direction relative to said carriage on an X-axis slide mechanism which is on said carriage;   moving said welding torch in a torch axis direction on a Y-axis slide mechanism which is on said carriage, to keep a torch height constant;   detecting a corner portion of a member material to be welded so as to enable the carriage to carry out a turning operation at the detected corner portion;   controlling an X-axis direction position and a Y-axis direction position of the welding torch by using an arc sensor;   setting said welding carriage at a weld start position relative to said material to be welded; and   controlling a travel direction of said welding carriage by means of a rough guidance controlling operation, said rough guidance controlling operation comprising: detecting an X-axis slide position of said welding torch when said welding torch is controlled to be positioned at a center of a welding groove by said arc sensor;   comparing said detected X-axis slide position with a preset reference value of said X-axis slide position of said welding torch;   calculating a differential value of said detected X-axis slide position of said welding torch; and   controlling an advancing direction of said welding carriage by supplying independently an adding speed signal to said pair of driving wheels, said adding speed signal being derived from outputs produced in said comparing step and said calculating step, so as to cause said carriage to run substantially parallel with said weld line and to keep a substantially constant distance between said carriage and said weld line, whereby said X-axis direction slide position of said welding torch is located at a proper position for welding.     
     
     
       14. The method of claim 13, comprising detecting said corner portion with a proximity switch. 
     
     
       15. The method of claim 14, wherein said step of detecting a corner portion comprises detecting a turning angle of said carriage by means of an encoder. 
     
     
       16. The method of claim 15, wherein said setting step comprises detecting said weld start position by a limit switch. 
     
     
       17. The method of claim 13, wherein said setting step comprises detecting said weld start position by a limit switch. 
     
     
       18. The method of claim 13, wherein said steps of moving said welding torch in said horizontal direction and in said torch axis direction are each carried out by a respective ball screw feed mechanism. 
     
     
       19. The method of claim 13, wherein said rough guidance controlling operation further includes: amplifying a speed signal which is calculated from a deviation of said X-axis slide position of said welding torch, to produce a first amplified signal; and   amplifying a signal which is a differentiated value of said X-axis slide position of said welding torch, to produce a second amplified signal;   said first and second amplified signals being coupled to said control unit.   
     
     
       20. The method of claim 19, wherein said speed signal and said signal which is a differentiated value are amplified by amplifiers having different gains. 
     
     
       21. The method of claim 19, wherein said controlling step of said rough guidance controlling operation includes respectively adding an initial speed (Vo) of said welding carriage to outputs from said first and second amplifiers to produce respective signals for driving respective driving motors of said driving wheels. 
     
     
       22. The method of claim 21, comprising outputting said initial speed from a standard welding speed setting unit. 
     
     
       23. The method of claim 21, wherein said driving wheels comprise a pair of inside drive wheels and a pair of outside drive wheels, and wherein said inside drive wheels are arranged closer to the welding groove than said outside drive wheels. 
     
     
       24. The method of claim 13, wherein said driving wheels comprise a pair of inside drive wheels and a pair of outside drive wheels, and wherein said inside drive wheels are arranged closer to the welding groove than said outside drive wheels. 
     
     
       25. A method of controlling a lattice welding robot during a welding operation, comprising: providing a self-driven welding carriage having a pair of driving wheels which can be controlled independently to run and turn said welding carriage, said carriage having a welding torch mounted on said carriage for rotating a welding wire at a torch tip end at a high speed;   moving said welding torch in a horizontal direction relative to said carriage on an X-axis slide mechanism which is on said carriage;   moving said welding torch in a torch axis direction on a Y-axis slide mechanism which is on said carriage, to keep a torch height constant;   detecting a corner portion of a member material to be welded so as to enable the carriage to carry out a turning operation at the detected corner portion;   setting said welding carriage at a weld start position relative to said material to be welded; and   controlling a travel direction of said welding carriage by means of a rough guidance controlling operation, said rough guidance controlling operation comprising: detecting an X-axis slide position of said welding torch;   comparing said detected X-axis slide position with a preset reference value of said X-axis slide position of said welding torch;   calculating a differential value of said detected X-axis slide position of said welding torch; and   controlling an advancing direction and speed of said welding carriage at said detected corner portion by supplying independently speeds signal to said pairs of driving wheels, said speed signals being derived from outputs produced in said comparing step and said calculating step, so as to cause said carriage to run along said weld line at a given speed at said detected corner portion and to keep a substantially constant distance between said carriage and said weld line at said detected corner portion, whereby said X-axis direction slide position of said welding torch is located at a proper position for welding.     
     
     
       26. The method of claim 25, comprising detecting said corner portion with a proximity switch. 
     
     
       27. The method of claim 25, wherein said step of detecting a corner portion comprises detecting a turning angle of said carriage by means of an encoder. 
     
     
       28. A method of controlling a lattice welding robot during a welding operation, comprising: providing a self-driven welding carriage having a pair of driving wheels which can be controlled independently to run and turn said welding carriage, said carriage having a welding torch mounted on said carriage for rotating a welding wire at a torch tip end at a high speed;   moving said welding torch in a horizontal direction relative to said carriage on an X-axis slide mechanism which is on said carriage;   moving said welding torch in a torch axis direction on a Y-axis slide mechanism which is on said carriage, to keep a torch height constant;   controlling an X-axis direction position and a Y-axis direction position of the welding torch by using an arc sensor;   setting said welding carriage at a weld start position relative to said material to be welded; and   controlling a travel direction of said welding carriage by means of a rough guidance controlling operation, said rough guidance controlling operation comprising: detecting an X-axis slide position of said welding torch when said welding torch is controlled to be positioned at a center of a welding groove by said arc sensor;   comparing said detected X-axis slide position with a preset reference value of said X-axis slide position of said welding torch;   calculating a differential value of said detected X-axis slide position of said welding torch; and   controlling an advancing direction of said welding carriage by supplying independently an adding speed signal to said pair of driving wheels, said adding speed signal being derived from outputs produced in said comparing step and said calculating step, so as to cause said carriage to run substantially parallel with said weld line and to keep a substantially constant distance between said carriage and said weld line, whereby said X-axis direction slide position of said welding torch is located at a proper position for welding.     
     
     
       29. The method of claim 28, wherein said setting step comprises detecting said weld start position by a limit switch. 
     
     
       30. The method of claim 28, wherein said steps of moving said welding torch in said horizontal direction and in said torch axis direction are each carried out by a respective ball screw feed mechanism. 
     
     
       31. The method of claim 28, wherein said rough guidance controlling operation further includes: amplifying a speed signal which is calculated from a deviation of said X-axis slide position of said welding torch, to produce a first amplified signal; and   amplifying a signal which is a differentiated value of said X-axis slide position of said welding torch, to produce a second amplified signal;   said first and second amplified signals being coupled to said control unit.   
     
     
       32. The method of claim 31, wherein said speed signal and said signal which is a differentiated value are amplified by amplifiers having different gains. 
     
     
       33. The method of claim 31, wherein said controlling step of said rough guidance controlling operation includes respectively adding an initial speed (Vo) of said welding carriage to outputs from said first and second amplifiers to produce respective signals for driving respective driving motors of said driving wheels. 
     
     
       34. The method of claim 33, comprising outputting said initial speed from a standard welding speed setting unit. 
     
     
       35. The method of claim 33, wherein said driving wheels comprise a pair of inside drive wheels and a pair of outside drive wheels, and wherein said inside drive wheels are arranged closer to the welding groove than said outside drive wheels. 
     
     
       36. The method of claim 28, wherein said driving wheels comprise a pair of inside drive wheels and a pair of outside drive wheels, and wherein said inside drive wheels are arranged closer to the welding groove than said outside drive wheels.